1. Field of the Invention
The present invention relates to a textured substrate for forming and growing an epitaxial film of an oxide superconductive material or the like, and more specifically to a textured substrate for forming an epitaxial film having good crystal orientation and adhesion.
2. Description of the Related Art
Materials having an epitaxial crystalline structure with a crystal orientation such as an oxide superconductive film and a solar cell film are used in various fields due to the specific properties thereof. Examples of the materials include oxide superconductive materials which compose superconductive conductors and superconductive shields for use in various types of electric power equipment. Materials having an epitaxial crystalline structure generally exhibit poor workability and the bulk material made therefrom has cost disadvantage in some cases. Accordingly, for use of the material, a thin film is often formed from the material on a predetermined substrate.
In order to allow a crystal having textured structure to epitaxially grow, a substrate for epitaxial film formation is required to have a surface with a textured structure. Examples of the substrate include a textured substrate formed of copper as a main constituent found by the present inventors (Patent Literature 1). The copper substrate for epitaxial film growth takes advantage of the easiness of controlling the copper crystal orientation, having a {100}<001> cubic texture with a deviation angle Δφ of crystal axis which satisfies an expression: Δφ≦6°. Although copper including no alloy element has insufficient strength, the problem was solved by cladding the substrate with a metal layer (base material) made of stainless steel or the like.
The present inventors made several modifications to the textured substrate for improving the quality of an epitaxial film to be formed thereon. For example, in a disclosed modification to the textured substrate having a copper layer, a thin film layer of nickel in a proper amount is laminated on the copper surface so as to further improve the crystal orientation (Patent Document 2).